On Sun, Oct 13, 2019 at 05:15:31PM +0800, Like Xu wrote:
> Exporting perf_event_pause() as an external accessor for kernel users (such
> as KVM) who may do both disable perf_event and read count with just one
> time to hold perf_event_ctx_lock. Also the value could be reset optionally.
> +u64 perf_event_pause(struct perf_event *event, bool reset)
> +{
> + struct perf_event_context *ctx;
> + u64 count, enabled, running;
> +
> + ctx = perf_event_ctx_lock(event);
> + _perf_event_disable(event);
> + count = __perf_event_read_value(event, &enabled, &running);
> + if (reset)
> + local64_set(&event->count, 0);
This local64_set() already assumes there are no child events, so maybe
write the thing like:
WARN_ON_ONCE(event->attr.inherit);
_perf_event_disable(event);
count = local64_read(&event->count);
local64_set(&event->count, 0);
> + perf_event_ctx_unlock(event, ctx);
> +
> + return count;
> +}
> +EXPORT_SYMBOL_GPL(perf_event_pause);
